demography, a fully formed science or a science in the making (1)
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8/17/2019 Demography, A Fully Formed Science or a Science in the Making (1)
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Demography, a Fully Formed Science or a Science in the Making? An Outline Programme
Author(s): Daniel Courgeau, Robert Franck, Julia KeyReviewed work(s):Source: Population (English Edition, 2002-), Vol. 62, No. 1 (2007), pp. 39-45Published by: Institut National d'Études DémographiquesStable URL: http://www.jstor.org/stable/27645292 .Accessed: 08/02/2012 20:50
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8/17/2019 Demography, A Fully Formed Science or a Science in the Making (1)
2/8
o
Daniel
Courgeau*
and
Robert
Franck**
Demography,
a
Fully
Formed Science
or a
Science
in
the
Making?
An
Outline
Programme
In
this
article,
we
examine
D.
Tabu
tin's
view
that
demography
has
certainly
become
a
science
in
the
true
sense
of the
word,
with its
body
of
research
objects,
methods and
paradigms.
We
also
attempt
to
understand
why
he nevertheless
goes
on
to state
that
demography
[is]
marking
time,
and still
just
as
hesitant
when it
comes
to
understanding
and
explaining.
We
then
go
on
to
(1.)
explore
the
subject
matter
of
demography,
(2.)
sketch
out
a
more
precise
programme
for the
discipline,
(3.)
examine its
paradigms
and
(4.)
stress
the value
of
amore
axiomatic
approach,
which would
reinforce
its
scientific
pertinence
and hence
its
reliability.
1.
The
object
of
demography
Is
the
concern
of
demography
the behaviour of
human
populations,
from
individual
to
society
level ,
as
Tabutin's
article
states? If
demography
went
down this
road,
it
would end
up
embracing
everything.
There
is
a
need,
we
feel,
to
resist the
temptation
to
spread
ourselves
too
thinly;
we
must
strive,
on
the
contrary,
to
focus
our
research
on
the
specific object
of
demography.
This
was
defined
long
ago
as
the trio
fertility,
mortality
and
migration.
Yet
by defining its specific object in this way the aim was not to restrict demography
to
the
study
of
hirths,
deaths
and
migratory
movements,
but rather
to
circumscribe
the
perspective
adopted by demographers
to
study
the
transformations
in
a
population.
These
transformations
are
many
and
varied,
but
they
are
partly
the result
of
growth
in
that
population,
its
decline,
or
stabilization.
The
specific
perspective
of
demography
is that
population
growth,
decline
and
stabilization
may
ultimately
be
explained by
a
particular
combination
of
fertility,
mortality
and
migration.
*
Institut
national
d'?tudes
d?mographiques.
**
Centre de
Philosophie
des
Sciences,
Universit?
catholique
de
Louvain.
Both authors
are
also
co-editors
of the
Methodos
Series,
published by Springer,
which
aims
to examine
and resolve the
main
methodological problems confronting
the social
sciences.
Translated
by
Julia
Key.
Population-^,
62
(1),
2007,
39-46
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4
D.
Courgeau,
R. Franck
This
sort
of
explanation
is not
causal.
It
can
be
compared
with
Galileo's
explanation
of the
acceleration of bodies
in
free
fall: such
acceleration
may
be
explained,
he
maintained, by
a
particular
combination
of the
distance
covered
and
the time
elapsed.
Yet
neither
time
nor
space
is
the
cause
of
the
acceleration
of
a
free-falling body.
Nevertheless,
it
is
the
combination of
these
two
which
gives
us
the universal
form
of
all
natural acceleration.
Space
and
time
are
the
parameters^
by
which
such acceleration
may
be
explained.
The
same
holds
true
for the
specific
object
of
demography. Fertility,
mortality
and
migration
are
the
set
of
parameters
by
which
we
seek
to
understand
the
basic form
of
growth,
decline
or
stabilization
of
any
given
population.
As for
the
empirical factors
(or
causes)
influencing population
growth,
decline
or
stabilization,
they
are
surely
countless and
extremely
varied,
at
both
individual and social levels
(Courgeau,
2003).
But
rather
than
exploring
them
all,
as
Tabutin's
article
recommends,
demographers ought
to
consider
only
those
which
are
thought
to
have
an
impact
on
the
combination
of
fertility,
mortality
and
migration
in
this
population;
it is
therefore
the
particular
perspective
of
demography,
its
specific object,
that
directs
the
empirical
investigations,
laying
down
a
clear
pathway through
the
jungle
of
facts.
2. An
outline
programme
Having
established
the
specific
object
of
demography,
or
its
particular
perspective
on
population
change,
we
can
clearly
see
the
two
main
tasks
facing
the
discipline.
The
first
-
as we
have
just
mentioned
-
is
to
determine
the
factors
influencing
the
combination
of
fertility,
mortality
and
migration
in
a
given
population
at
a
certain
point
in
time,
in
the
hope
of
controlling
its
growth,
decline
or
stabilization.
The
second,
yet
more
ambitious,
is
to
ascertain
the
general
structure
of
the
combination of
fertility,
mortality
and
migration,
in
other
words
the
principle
of
all
demographic
growth
and
decline
(just
as
the
law
of
Galileo
gives
us
the
principle
of
all
natural
acceleration).
As
far
back
as
1760,
Euler
sought
to
establish
the
bases of
such
a
principle,
which
were
then
generalized
by
Lotka in 1939, and
subsequently
by
Preston and Coale in 1982.
These
developments
show
us
the
way
forward.
They
enable
us to
establish
what
Bourgeois-Pichat
(1994)
termed
the
fundamental
equation
of
population
dynamics ,
although
this
is
only
valid
under
the
hypotheses
of
the
cross
sectional
paradigm,
which
we
will
examine
below.
These
two
tasks
outline
an
agenda
for
demography
which
holds
nothing
new
but
which
dictates
that
demographic
research be
centred
on
the
further
development,
both
empirical
and
theoretical,
of
its
specific
object.
In
contrast,
if
this
specific
object
is
lost
to
sight,
and
replaced
with
the
behaviour
of
human
populations, from individual
to
society level ,
as
Tabutin proposes, one could
be
led
to
believe
that,
in
order
to
explain
a
demographic phenomenon,
all
(1)
The
term
is taken
from
E
Suppe
(1989).
I
40
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Demography,
a
Fully
Formed
Science
or a
Science
in the
Making?
)
observable
population phenomena
must
necessarily
be
analysed.
Furthermore,
this
approach
overlooks
the theoretical mission
of
demography,
an
integral
part
of
its
scientific
status.
Reinstating
the
specific
object
of
demography
thus
presents
a
twofold
challenge
-
that
of
guarding
against
the
fragmentation
of
demographic
research
while also
protecting
its
scientific
status.
Tabutin maintains that
demography
has
certainly
become
a
science
in
the
true
sense
of
the
word,
with
its
body
of
research
objects,
methods
and
paradigms.
We
believe rather that
demography
is
a
science
in
the
making.
In
the
sections
that
follow
we
will
examine
what
more
must
be done
to
complete
the
process.
We
thus
hope
to
fulfil the
request
from the editorial
committee
of
Population
for
a
viewpoint
on
the
future
of
demography.
Two
points
merit
particular
attention. The first concerns the
ways
inwhich
the
phenomena
observed
within
a
population
are
related
to
the
set
of
key
parameters
(fertility,
mortality
and
migration)
used
in
demography
to
explain
population growth,
decline
or
stabilization.
There
are
several different
ways
of
relating
these
phenomena
to
the
specific object
of
demography,
and
each
of
them
follows
a
paradigm.
For
demography
to
become
a
fully
formed
science,
it is
important
to
identify
these
paradigms correctly,
to
use
them
well,
to
improve
them
and
to
exploit
their
potential
fully.
3.
The
paradigms
The
specific
object
of
a
science
-
its
scientific
object
in
the
sense
of
G.G.
Granger
(1994)
-
does
not
initially
have
an
explicit, general
definition.
Sciences
such
as
physics
and
biology,
for
example,
evolve
as
a
series
of
successive
explanations
of their
object,
as
illustrated
by
the
transition
from
Newtonian
physics
to
Einstein's
general
theory
of
relativity.
In
the
same
way,
the
object
of
demography
is made
clear
through
successive
paradigms,
which
describe
the various
types
of
relationship
between the
phenomena
observed
and
the
scientific
object.
Once again, Tabutin clearly states that there are paradigms in demography,
but
he
does
not
further
specify
what he
understands
by
this
term,
which
has
many
different
meanings,
and he
certainly
does
not
link them
to
the
object
of
the
discipline.
This
is
what
we
will
attempt
to
do here.
Firstly,
the notion
of
paradigm
that
we use
here
differs
slightly
from those
proposed
by
Kuhn
(1970),
and
in
fact
answers
the
following
question:
how
can
we move
from
events
experienced
to
scientific
object,
as we
understand
it
here?
The
process
of
elaborating
answers to
this
question
is
what
generates
the
various
paradigms
that have
appeared throughout
the
history
of
demography;
the
following
detailed
analysis
of the
relationships
between scientific
object
and
phenomena
observed
will
show
clearly
the vital role
they play.
It is
simply
not
possible
to
expand
upon
the
various
paradigms
in
a
short
commentary
such
as
this
(Courgeau,
2003, 2004,
2007),
but
we
will
point
out
more
precisely
how
they
differ and what features
they
share.
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D.
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R. Franck
According
to
the cross-sectional
paradigm,
social
phenomena
are
independent
of
individuals and
can
be
explained
by
various
economic,
political,
religious
and social
characteristics,
among
others,
of
the
society
in
which
these individuals
live.
From
this
one can
derive,
firstly,
a
fundamental
equation
of
population
dynamics,
linking
variation
over
time
of
cross-sectional
measurements
of
fertility, mortality
and
migration
-
which
are
mutually
independent
-
and,
secondly,
an
aggregate
regression
method
to
link
these
phenomena
to
various
characteristics
of
the
population.
With the
longitudinal
paradigm,
the
aim is to
study
the
occurrence
of
one
single
event,
during
the
lifetime of
a
generation
or
cohort,
in
a
population
that
retains
the
same
characteristics
for
as
long
as
the
phenomenon
persists.
As
with the
cross-sectional
paradigm,
the
population
must
therefore be
considered
homogeneous,
and the
phenomena
mutually
independent.
This
time,
however,
the
only comparisons
are
between
homogeneous
groups
followed
throughout
their
life
course.
We
have
a new
type
of
fundamental
equation:
macro-simulation
methods
can
be used
to
simulate
the
evolution of
such
a
population,
and
longitudinal
analysis
methods
to
study
their
trajectory
over
time.
The
event
history
paradigm
holds
that,
over
the
life
course,
individuals
follow
a
complex trajectory
which
depends
at
any
given
time
on
their
previous
life
course
and
on
any
information
they
may
have
acquired
in
the
past.
The
population
then
becomes
heterogeneous,
and
demographic
phenomena
become
interdependent. In view of this interdependence, a fundamental equation of
any
sort
is
no
longer
possible,
although
micro-simulation
methods
serve as
both
theoretical and
empirical
models
applicable
to
demography,
and
event
history
analysis
methods
link
demographic phenomena
to
one
another,
as
well
as
to
various
characteristics of
the
population.
Finally,
the multilevel
paradigm
goes
beyond
the
opposition
between the
holism of the
cross-sectional
or
longitudinal approach
and the
methodological
individualism
of the
event
history approach,
for
it
holds
that
human
behaviour
can
only
really
be
understood
by
bringing
different
levels
of
aggregation
into
play.
Each
of
the
previous paradigms
offered
only
a
narrow
focus
on
its
own
objects,
and
each of
them has
been
proven
perfectly
consistent with
regard
to
these
objects,
as
a
number
of
demographic
analyses
have demonstrated
over
time.
Yet
equally,
the
reason
why
it
is
difficult
to
move
from
one
paradigm
to
another
is
that such
objects
differ,
at
least
in
part.
In
particular,
these
objects
are
linked
in
different
ways
to
the
phenomena
observed,
and the
assumed
relationships
between
them
are
highly
dependent
upon
the
paradigm
used:
objects
considered
in
absolute
time
(civil
calendar)
versus
objects
considered
in
relative
time
(individual
calendar);
population
homogeneity
under the
cross
sectional and
longitudinal
paradigms,
versus
heterogeneity
under
the
event
history
paradigm; independent
phenomena
under
the
longitudinal
paradigm
yet
a
high
degree
of
dependence
under
the
event
history paradigm;
non-existence
of levels
versus
existence
of
levels under
the
multilevel
paradigm,
etc.
This
explains
the
inconsistencies
sometimes
observed,
depending
on
the
type
of
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Demography,
a
Fully Formed Science
or a
Science
in the
Making?
)
analysis
performed,
but
at
the
same
time
reveals that certain
findings
may
in
fact
be
complementary
-
a
multilevel
analysis
may
complement
a
cross-sectional,
longitudinal
or
event
history analysis.
A
multilevel
approach
would
therefore
seem to
offer
a
useful
synthesis
of
the
previous paradigms,
in
that
it
replicates
some
of their
results
and
provides
an
explanation
of them
-
certain
effects
are
linked
to
society,
while others
are
more
related
to
the individual.
In
the
light
of
this,
the truth
of
the
following
statement
becomes self-evident:
The human fact
can
indeed be
scientifically
understood
only
through
multiple
angles
of
vision,
but
on
condition
that
we
discover
the controllable
operation
which
uses
these
angles
to recreate
it
stereoscopically. (Granger,
1994)
Yet
we
believe
it is
still
too
early
to
affirm
that
demography
has
already
explored
all
possible
angles
of vision; the links between
types
of behaviour
observed
at
different levels
of
aggregation
have
not
yet
been
properly investigated.
For
example,
individuals
acting
in
isolation
might
alert
a
whole
community
to
a
problem affecting
all
of
its
members,
which
may
in
turn
result
in
political
measures at a
higher
level,
and
so
forth.
4. An
axiomatic
approach
Our
second
key
point
concerns
the need
for
an
axiomatic
approach
to
demography
to
strengthen
its
scientific
validity.
An
axiom is
nothing
other
than a principle; it sets out the general conditions without which the phenomena
one
is
seeking
to
explain
would
not
be
what
they
are,
or
would
not
take
place
in
the
way
that
they
do.
The Galilean law
governing
the
acceleration
of
bodies,
as
mentioned
above,
is
one
example
of
an
axiom,
as are
the
well-known
axioms
of
Euclid.
One
might
say
that
the three
parameters
o?
fertility,
mortality
and
migration,
i.e.
the
scientific
object
of
demography,
are
in
themselves
a
first
step
towards what
we
might
call
the axiomization of
demography,
for
it is
indeed
this
trio
that
provides
us
with
the
conceptual
framework
by
which
we
may
hope
to
grasp
the
principle
of
all
population
growth,
decline
or
stabilization.
The basic
form
of
quantitative
transformations
in
any given population
lies
in
a
particular
combination
of
fertility,
mortality
and
migration;
without
this
form,
none
of
the
quantitative
transformations observed would
be
possible.
We
still
do
not
know,
however,
what
this
combination
is.
A
scientific
discipline
generally
includes
several
complementary
axioms
or
principles
to
explain
more
fully
the
phenomena
studied.
The axiomization
of
demography
is
not
confined
to
the
search for the
fundamental
equation
of
all
population
growth,
decline
and
stabilization.
More
specific
axioms should
also
be
on
the
agenda,
and
clarifying
the
paradigms
that
we
mentioned
above
will
help
us
to
discover them.
What differentiates
a
theory
from
an
axiom? The word
theory,
as we
know,
suffers
badly
from
multiple
meaning
syndrome
-
it is
now
habitual
to
consider
any
freely
conceived
explanatory
hypothesis
as a
theory
if
it
can
subsequently
be tested
by
means
of observation
and
statistical
calculation
(confirmatory
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4
D.
Courgeau,
R. Franck
analysis).
An
axiom,
on
the
other
hand,
is
necessarily
the result
of
observation
,
since it
defines
the
general
conditions
implied
by
the
phenomena
one
is
seeking
to
explain;
the conditions without which
these
phenomena
would
not
he what
they
are,
or
would
not
take
place
as
they
do.
Only
the
phenomena
can
tell
us
what
they
imply(3),
they
are
the
necessary
route
to
axioms.
Galileo's
law
is
one
such
example.
In
the
light
of
this,
it is
easy
to
see
how
a
more
axiomatic
approach
can
also
reinforce the
scientific
pertinence
of
demography,
and hence
its
reliability.
Such
a
shift
involves
refocusing
empirical
research
on
what is
implied
by
phenomena,
a
more
demanding
empirical
task than
simply
confirming
or
refuting
-
with the
attendant uncertainties
-
successive
explanatory
models.
Yet
at
the
same
time,
it
inserts
theoretical
research
in
empirical
investigation,
and rescues
theory
from the confusion of ideas in which it is all too often
confined(4).
(2)
Although
not
what is
usually
said of
axioms,
this
was
firmly
asserted
by
the
fathers
of
modern
science
(Francis
Bacon,
Galileo,
Ren?
Descartes,
Isaac
Newton,
etc.).
For
more
on
this,
see
R. Franck
(2007).
(3)
This
is
the
true
meaning
of classical
induction,
which
has
been
distorted
by
the
philosophical
tra
dition born
of
David
Hume.
(4)
For
more
on
how
to
combine
empirical investigation
and
theoretical
research,
see
R.
Franck,
ed.
(2002).
i
44
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8/8
Demography,
a
Fully
Formed
Science
or
a
Science
in the
Making?
)
4?
References
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45
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